I own civic ek sedan with D16Y4 engine with auto transmission. I have installed performance headers 4-2-1 after installation I faced an issue during low rpm (during heavy traffic), engine started to vibrate and then lose power and throttle response gets dead if I push throttle to half way it makes engine stop and during high rpm it's performance is awesome. While in neutral car remains normal. Headers details, Diameter of 4 pipes is 1.75" while 2 pipes diameter is 2" and reset of measurement is same as 2" pipe. O2 sensor is installed at end of headers pipe.
How I overcome this issue? Thanks in advance